Growing
Marigolds Don't Repel Most Garden Pests the Way Gardeners Assume
The marigold pest-repellent reputation is a real, narrow finding stretched into a much bigger claim than the evidence supports.
The genuine research behind marigolds involves certain species, particularly French marigold (Tagetes patula), releasing compounds from their roots that suppress some species of root-knot nematodes in the soil around them — a real, measurable, but narrow effect that also usually requires a full season of marigolds grown as a dense cover crop, not a few plants dotted between vegetables.
The broader claim that marigolds repel aphids, whiteflies, or beetles above ground has far weaker support; some studies find marginal effects, others none, and interplanting for general 'pest control' likely does more for pollinator visits and garden diversity than for measurable pest suppression.
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